I've also only been a lurker. This sale has definitely opened my eyes as well. I've always been a Steam user (and always prefer a steam key to any other type of purchase), but while GoG doesn't match Steam's convenience (buy on phone, deploy from phone, come home to find game ready to play), the community here is very different, and I wasn't aware of that until this sale.
While I didn't like that due to the seemingly random fleeting nature of the sale, I missed out on one of my targets (though very luckily got all the others, including NWN2 which was number one on my list and seemed to fly by), it was that same nature that kept me glued to GoG (seemingly at the expense of my real world responsibilities), and to follow threads like this to see what games had come and gone.
To be honest, before this sale, I wasn't aware that GoG even HAD a forum. It was just a vending machine to me.
I also didn't know that GOG had a forum. Especially one with such awesome and caring members. I missed out on RCT3, but managed to snag a few other great games to occupy my time. I tend to have a lurker personality, but I will try to come out more to interact with other GOG'ers.